Chelsea have won three league games in a row without conceding a goal since coach Antonio Conte changed formation to play with three at the back.
Cahill said: “We can’t get carried away after what happened against Manchester United. We are still getting accustomed to this new formation.
“At the moment it is proving difficult to play against. We have managed to play out from the back well and if we press high, we can cause trouble with the wing backs.
“We are learning as we’re going along but we are adapting the more we use the system.
He added: “Of course we can be one of the teams fighting for the title. But we are not thinking about winning it right now.”